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31.
Cities lead the way in climate-change action 总被引:2,自引:0,他引:2
32.
An Inhomogeneous Hidden Markov Model for Efficient Virtual Machine Placement in Cloud Computing Environments 下载免费PDF全文
In a cloud environment virtual machines are created with different purposes, such as providing users with computers or handling web traffic. A virtual machine is created in such a way that a user will not notice any difference from working on a physical computer. A challenging problem in cloud computing is how to distribute the virtual machines on a set of physical servers. An optimal solution will provide each virtual machine with enough resources and at the same time not using more physical services (energy/electricity) than necessary to achieve this. In this paper we investigate how forecasting of future resource requirements (CPU consumption) for each virtual machine can be used to improve the virtual machine placement on the physical servers. We demonstrate that a time‐dependent hidden Markov model with an autoregressive observation process replicates the properties of the CPU consumption data in a realistic way and forecasts future CPU consumption efficiently. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
33.
Summary The muscle enzyme calpain II, in contrast to muscle calpain I, was markedly inhibited by millimolar concentrations of the polyamines spermine and spermidine. These compounds and the calpain inhibitor calpastatin had synergistic inhibitory effects on calpain II. These results suggest that the polyamines may have possible regulatory effects on the in vivo activity of calpain II enzymes. 相似文献
34.
Summary Electrical impedance and outside tip diameter of glass microelectrodes were measured. With outside tip diameters smaller than 0.7 there was a significant deviation between calculated and measured values. The relationship between outside tip diameter and wall thickness was investigated electronmicroscopically on micropipettes filled with phosphotungstic acid.
Mit Unterstützung des Schweizerischen Nationalfonds, Projekt Nr. 2903. 相似文献
Mit Unterstützung des Schweizerischen Nationalfonds, Projekt Nr. 2903. 相似文献
35.
Correlations are generally described by one of two mechanisms: either a first event influences a second one by sending information encoded in bosons or other physical carriers, or the correlated events have some common causes in their shared history. Quantum physics predicts an entirely different kind of cause for some correlations, named entanglement. This reveals itself in correlations that violate Bell inequalities (implying that they cannot be described by common causes) between space-like separated events (implying that they cannot be described by classical communication). Many Bell tests have been performed, and loopholes related to locality and detection have been closed in several independent experiments. It is still possible that a first event could influence a second, but the speed of this hypothetical influence (Einstein's 'spooky action at a distance') would need to be defined in some universal privileged reference frame and be greater than the speed of light. Here we put stringent experimental bounds on the speed of all such hypothetical influences. We performed a Bell test over more than 24 hours between two villages separated by 18 km and approximately east-west oriented, with the source located precisely in the middle. We continuously observed two-photon interferences well above the Bell inequality threshold. Taking advantage of the Earth's rotation, the configuration of our experiment allowed us to determine, for any hypothetically privileged frame, a lower bound for the speed of the influence. For example, if such a privileged reference frame exists and is such that the Earth's speed in this frame is less than 10(-3) times that of the speed of light, then the speed of the influence would have to exceed that of light by at least four orders of magnitude. 相似文献
36.
Is animal culture a real entity or is it rather just in the eye of the beholder? The concept of culture began to be increasingly used in the context of animal behaviour research around the 1960s. Despite its success, it is not clear that it represents what philosophers have traditionally thought to be a natural kind. In this article I will show, however, how conceiving of animal culture in this fashion has played a role in the “culture wars”, and what lessons we can draw from this. First, an analysis of the epistemological landscape of author keywords related to the concept of animal cultures is presented, thus vindicating the centrality of the concept in describing a broad range of findings. A minimal definition that encompasses the multiple strands of research incorporating the notion of culture is proposed. I then systematically enumerate the ways in which culture thus conceived cannot be considered a natural kind in the study of animal behaviour. This is accomplished by reviewing the efforts and possibilities of anchoring the elusive idea in specific mechanisms, homologies, selection pressures, homeostatic property clusters, or alternatively, its reduction or elimination. Finally, a plausible interpretation of the scientific status of the animal culture concept is suggested that is compatible with both its well established use in animal behaviour research and its inferential limitations. Culture plays the role of a well-established epistemic kind, a node that connects different areas of research on common themes. 相似文献
37.
Lgr5 marks cycling, yet long-lived, hair follicle stem cells 总被引:1,自引:0,他引:1
Jaks V Barker N Kasper M van Es JH Snippert HJ Clevers H Toftgård R 《Nature genetics》2008,40(11):1291-1299
In mouse hair follicles, a group of quiescent cells in the bulge is believed to have stem cell activity. Lgr5, a marker of intestinal stem cells, is expressed in actively cycling cells in the bulge and secondary germ of telogen hair follicles and in the lower outer root sheath of anagen hair follicles. Here we show that Lgr5(+) cells comprise an actively proliferating and multipotent stem cell population able to give rise to new hair follicles and maintain all cell lineages of the hair follicle over long periods of time. Lgr5(+) progeny repopulate other stem cell compartments in the hair follicle, supporting the existence of a stem or progenitor cell hierarchy. By marking Lgr5(+) cells during trafficking through the lower outer root sheath, we show that these cells retain stem cell properties and contribute to hair follicle growth during the next anagen. Expression analysis suggests involvement of autocrine Hedgehog signaling in maintaining the Lgr5(+) stem cell population. 相似文献
38.
Hugo Theorell 《Cellular and molecular life sciences : CMLS》1948,4(3):100-109
Ohne ZusammenfassungHauptreferat, gehalten vor der Schweizerischen Medizinisch-Biologischen Gesellschaft in Genf am 31. August 1947, anläßlich der 127. Generalversammlung der Schweizerischen Naturforschenden Gesellschaft. 相似文献
39.
V. J. Csernus T. Hammer D. Peschke E. Peschke 《Cellular and molecular life sciences : CMLS》1998,54(7):733-743
Insulin secretion from isolated pancreatic islets of 8- to 12-day-old rats was investigated in a dynamic in vitro (perifusion)
system. The aims of the study were (i) to describe a carefully controlled in vitro method to study the mechanism of insulin
secretion and to analyse the effects and dynamic interactions of bioactive compounds on isolated rat pancreatic islets, (ii)
to validate the method by comparing fundamental data on the functions of the islets obtained with this method to those collected
with other techniques; and (iii) to find novel features of the control of insulin secretion. The method was carefully designed
to maintain the functional capacity of the explanted cells. A functional standardization system was elaborated consisting
of (i) analysis of the changes in the basal hormone secretion of the cells; (ii) evaluating responses to a standard, specific
stimuli (50 mM glucose for 3 min); (iii) determining the alteration of the momentary size of the hormone pool with responses
to KCl; and (iv) direct determination of the total intracellular hormone content from the extract of the column. The technique
provides accurate quantitative data on the dynamic responses to biologically active compounds that act directly on the pancreatic
islets. The islets maintained their full responsiveness for up to 7 days, and responses as close as in 1-min intervals could
be distinguished. A linear dose-response relationship was found on the glucose-induced insulin release in case of 3-min stimulation
with 4 and 500 mM of glucose (lin-log graph). Utilizing this method, we showed that no desensitization to glucose-induced
insulin release can be observed if the responsiveness of the cells is properly maintained and the parameters of the stimulation
are carefully designed. Exposure of the explanted islets to 10 μM acetylcholine or 30 mM arginine (Arg) induced a transitory
elevation of insulin release similar in shape to that experienced after glucose stimulation. Norepinephrine (NE), dopamine
(DA) and somatostatin (SS) did not induce any detectable alteration on the basal insulin secretion of the islets. However,
100 nM SS given together with 50 mM glucose, 30 mM Arg or 10 μM acetylcholine significantly reduced the insulin-releasing
effect of these substances (by 75.5, 71.5 and 72.5%, respectively). At the same time, SS did not alter the insulin response
of the islets to 100 mM elevation of K+ concentration. SS also inhibited glucose-induced insulin release in a dose-dependent way (ED50 = 22 nM). A similar dose-dependent inhibitory effect on glucose-induced insulin release was found with NE (ED50 = 89 nM) and DA (ED50 = 2.2 μM). γ-Aminobutyric acid (GABA) did not influence insulin release under similar circumstances.
Received 16 January 1998; received after revision 6 May 1998; accepted 8 May 1998 相似文献
40.
Atherogenesis in transgenic mice expressing human apolipoprotein(a) 总被引:10,自引:0,他引:10
Elevated plasma levels of the lipoprotein Lp(a) are associated with increased risk for atherosclerosis and its manifestations, myocardial infarction, stroke and restenosis (for reviews, see refs 1-3). Lp(a) differs from low-density lipoprotein by the addition of the glycoprotein apolipoprotein(a), a homologue of plasminogen that contains many tandemly repeated units which resemble the fourth kringle domain of plasminogen, and single homologues of its kringle-5 and protease domain. As plasma Lp(a) concentration is strongly influenced by heritable factors and is refractory to most drug and dietary manipulation, the effects of modulating it are difficult to mimic experimentally. In addition, the absence of apolipoprotein(a) from virtually all species other than primates precludes the use of convenient animal models. Here we show that transgenic mice expressing human apolipoprotein(a) are more susceptible than control mice to the development of lipid-staining lesions in the aorta, and that apolipoprotein(a) co-localizes with lipid deposition in the artery walls. 相似文献